1. Field of the Invention
This invention relates to a switch device which is suitably applicable as, for instance, a dimmer switch device of one position type for a motor vehicle.
2. Related Art
An example of a dimmer switch device of one position type for a motor vehicle has been disclosed by Unexamined Japanese Utility Patent Application No. 27931/1989. The dimmer switch device is designed as shown in FIG. 4. That is, an operating member 2 is provided on a switch body 1 in such a manner that it is vertically movable and is urged upwardly by a coil spring 3 interposed between the switch body 1 and the operating member 2. An operating piece, namely, a push rod 4 is provided at the center of the lower surface of the operating member 2. The push rod 4 is moved along a straight line A together with the operating member 2. When the operating member 2 is pushed from above by an operating lever 5, the operating member 2 is moved downwardly; and when the operating lever 5 is released, the operating member 2 is returned to its original position (as shown in FIG. 4) by the elastic force of the coil spring 3. More specifically, the push rod 4 is also returned to its original position together with the operating member 2. That is, the push rod 4 is an automatic return type operating piece.
Below the push rod 4, a swinging member, namely, a dimmer cam 6 is swingably mounted on a shaft 7. An accommodating chamber 6a is formed in the lower end portion of the dimmer cam 6, in which an articulation piece 8 is accommodated. The articulation piece 8 is urged outwardly by a coil spring 9 interposed between the bottom of the accommodating chamber 6a and the articulation piece 8. Below the dimmer cam 6, a V-shaped articulation member 10 is provided with which the articulation piece 8 is in contact. The V-shaped articulation member 10 has a top 10a and two slopes 10b and 10c.
When the lower end of the articulation piece 8 abuts against the right slope 10b of the V-shaped articulation member 10 while the right end portion 6b of the dimmer cam 6 engages with a regulating part of the switch body 1, the dimmer cam 6 takes a first swing position as shown in FIG. 4. When, under this condition, the operating member 2 together with the push rod 4 is depressed by the operating lever 5, the lower end portion of the push rod 4 is abutted against the upper right slope and right recess 6c of the dimmer cam 6 to push the latter 6. As a result, the dimmer cam 6 is turned (swung) clockwise (in FIG. 4) about the shaft 7; that is, the lower end portion of the articulation piece 8 is moved over the top 10a of the V-shaped articulation member 10, and brought into contact with the left slope 10c of the latter 10 while the upper left portion 6d of the dimmer cam 6 is engaged with another regulating part of the switch body 1. Thus, the dimmer cam 6 is held at a second swing position which is located symmetrical with the first swing position shown in FIG. 4.
When, under the condition that the dimmer cam 6 is held at the second swing position, the operating member 2 together with the push rod 4 is depressed by the operating rod 5, the lower end of the push rod 4 is abutted against the upper left slope and left recess 6e of the dimmer cam 6 to push the latter 6. As a result, the dimmer cam 6 is swung in the opposite direction (counterclockwise) to the first swing position. That is, the dimmer cam 6 takes the first and second swing positions alternately whenever pushed by the push rod 4.
A dimmer change-over switch operating in association with the swing of the dimmer cam 6 is designed as follows: When the dimmer cam 6 is at the first swing position, the contact mechanism operates to select a high beam is obtained; and when the dimmer cam 6 is at the second swing position, the contact mechanism operates to select a low beam. That is, whenever the operating lever 5 is operated by the operator; in other words, whenever the operating member 2 together with the push rod 4 is depressed, the dimmer change-over switch is operated to switch the high beam and the low beam over to each other.
In the above-described conventional switch device, as shown in FIG. 4, the push rod 4, the axis of the shaft 7 of the dimmer cam 6, and the top 10a of the V-shaped articulation member 10 are on one and the same straight line A. Hence, depending on the way of operation of the operating lever 5, as shown in FIG. 5 the lower end of the articulation piece 8 of the dimmer cam 6 is set on the top 10a of the V-shaped articulation member 10; that is, the dimmer cam 6 is stopped at the neutral position. Even if, in this case, the operating lever 5 is operated to push the operating member 2 and the push rod 4 downwardly, the dimmer cam 6 may be held at the neutral position, because the lower end of the push rod 4 merely abuts against the top 6f of the dimmer cam 6, to push the latter. Hence, in this case, in order to swing the dimmer cam 6 to the first or second swing position, it is necessary to operate the operating lever 5 repeatedly.